This invention relates to roadway markers that are used for traffic lane delineation, in particular, to markers with simplified, low cost structural body.
Roadway markers are used on pavements along centerlines, edge lines, lane dividers, near fire hydrants or guardrail. Other roadway markers are used as temporary lane dividers during construction phases. The most commonly used retro-reflective roadway markers using a housing filled with structural polymeric material are based on Heenan U.S. Pat. No. 3,332,327, Balint U.S. Pat. No. 3,409,344, or Hedgewick U.S. Pat. No. 5,002,424.
Typically, these types of markers are produced in a process consisting of three to four steps: Firstly, injection molding of a thermoplastic housing (shell), integrally molded with one or two reflective faces.
Each inclined reflective face, integrally having multiple of cube corner reflective elements within the inside surfaces of the optically transparent housing (shell).
Secondly, either the reflective faces within a shell or the entire inside surface of the shell can be coated with a reflective metallic sealer by a process known as vacuum metalizing. This metallic sealer is needed to seal the cube corner reflective elements so they retain part of their retro-reflectivity prior to the next step of filling the shell with a thermosetting resinous material, such as epoxy or polyurethane to form a rigid structural body.
This resinous filler material encapsulates the metalized cube corner reflective elements and agglutinate to interior surfaces of said housing, thereby provide the marker the impact resistant structural body.
Finally, a layer of relatively course sand or glass beads are dispersed over the outer surface of the filler material prior to solidification of the filler material. Part of the sand particles will remain partially protruding above the planar surface of the marker base, thereby increasing the adhesive welding parameter of the base surface.
These types of markers worked well for six or seven months, however, due to poor abrasion and incompatibility of the shell material to the resinous filler material causes pealing of the reflective face or the shell, thereby losing retro-reflectivity. A major disadvantage of this type of structural body is that epoxy or urethane liquid fill systems are expensive, inconsistence in quality and environmentally unfriendly.
Another major development in the pavement marker art has been made; this was achieved by eliminating the use of the metalized sealer for the cube corner reflective elements.
U.S. Pat. No. 4,726,706 to Attar, which is incorporated herein by reference in its entirety, divide the inside surfaces of the reflective faces into reflective cells, each cell will have multiple cube corner reflective elements, the cells are isolated from each other by partition and load carrying walls. However, instead of metalizing the inside surfaces, all inside surfaces of the reflective faces has to be sealed by a thin sheet prior to filling the shell with resinous structural polymers.
Likewise PCT/US2001/0048847 A1 to Khieu discloses a shell housing either integrally made having multiple cube corner reflective elements within two inclined faces or a sheet of reflective elements adhered to said inclined faces. The entire inside surface with the cube corner reflective elements must be sealed with a thin sheet prior to filling the housing with resinous material.
U.S. Pat. No. 6,126,360 to May discloses pavement marker having unfilled shell (housing) and lower base plate with load carrying walls.
The housing (shell) is made of a composite material having two inclined faces. Each inclined face is integrally formed with recessed area (12b) and (12c). Each recessed area having multiple load-carrying wall (22) defining hollow cavity recesses (24).
A lens member (50) is welded to the load carrying walls (22) within the recessed areas (12b) and (12c) of the marker housing prior to welding the base plate (314).
The goal of this invention is to have a durable roadway marker with high reflectance, low cost and utilizing the presently used shell like housing that is monolithically formed including at least one inclined reflective face with multiple cube corner reflective elements and without the need to weld a lens sheeting to a sealed, recessed portion of a housing, or without the need to seal the reflective elements with a thin sheet prior to filling the housing. This invention also eliminates the need to fill the housing with resinous filler material.
This invention provides a novel process of forming one piece, hollowed structural body that can replace the potting process for a typical epoxy filled reflective pavement markers having one piece upper housing (shell). The present invention also eliminates the process of sealing the lens surfaces either within a secondary sealed, recessed regions of a housing or sealed with a thin sheet of plastic. This method provides a monolithically injection molded, one-piece, hollowed structural body with a sealed and textured base area that provides large welding parameter, thereby providing better adhesion to the pavement and higher resistance to flexural stresses. The one-piece hollowed structural body provides integrally formed load carrying walls that can be welded directly to a portion of the apexes of the cube corner reflective elements, while retaining the apexes of the remaining cube corner elements freely within air gaps inside the hollow cavities defined by said load carrying walls.
Alternatively, if a housing (shell) such as Attar""s 706 is used, the inside raised partition walls defining the reflective cells within each reflective face can be used for agglutination onto said one-piece structural body which is fabricated to match Attar""s 706 housing interior.
The primary objective of this invention is to provide a process of manufacturing one-piece structural body, thereby replacing the process of potting the housing with a resinous filler material and pre-sealing the lens surfaces.
Another objective of this invention is to provide a raised roadway marker made of high impact resistant material without the need to use composite material.
The surface of this reflective pavement marker can be abrasion resistant with high reflective index. The present invention further provides a method of making two-piece raised roadway marker of any desirable shape and configuration, such as, a marker with truncated body.
In accordance with still further aspects of this invention, the marker can be made for one or two way traffic usage. Having an integrally built-in cube corner reflective elements provides durability and cost effectiveness.